A centralized state is important for the liege to grow powerful, but a decentralized state might be easier to maintain (or necessary, if the liege has many direct vassals). If the Conclave DLC is activated, this law is found under the Realm laws tab.

Tribal organization applies to independent tribal rulers and replaces crown laws. It can only be changed one increment at a time, but unlike crown law a ruler may change it more than once in their lifetime.

With the Charlemagne DLC, independent feudal emperors can grant kingdoms or duchies to vassals as Viceroyalties. Unlike regular titles, viceroyal titles automatically revert to the liege upon their holder's death, lessening the chance that vassals will grow too powerful or pass their titles on to disloyal heirs. If the Conclave DLC is activated, this law is found under the Realm laws tab.

Note that each kingdom viceroyalty you create will generate -2 approval from all of your feudal vassals (not including other viceroys) and duchy viceroyalties will give a -1 opinion. The stacking of this negative approval can be problematic if you use viceroyalties often.

Note that if you are an emperor and don't see an option within Demesne Laws / Realm Laws to choose between "Feudal Administration" and "Imperial Administration", you may need to scroll down to see those options.

Note that Imperial Administration automatically gains ability to have kingdom and duchy viceroys, regardless of legalism. This may be considered a bug and changed in a later update.